How Long Will an Engine Last With Blow-By?

You have most probably seen or heard blow-by on the road. Well, that can be because blow-by can occur to all types of engines, even the new ones. When it arises, it requires immediate action lest it results in other costly repairs and damages.

With blow-by, the engine life, performance, and overall efficiency are severely affected. The recommended rebuild life for such an engine is about 11000 hours. However, with the consequent damages and failures resulting from carbon buildup and piston wear, this will be about 3000 to 4000 hours. 

This article explains the catastrophic damages that result from engine blow-by, and what you can do to fix it. 

How Long Will an Engine Last With a Blow-By?

Typically, blow-by is the phenomenon where the cylinder pressure gets too high and escapes past the piston rings, and gets into the crankcase. The first noticeable signs will be some glazing on the cylinder or carbon forming on the top ring grooves. Eventually, there is more internal engine stress which affects its performance.

The recommended rebuild life for an engine affected by a blow-by is approximately 11,000 hours. The consequent failures due to carbon buildup can give you about 3000 to 4000 hours. The typical rebuild intervals lie at 8000 to 10000. 

Increased exhaust soot as a result of neglecting blow-by damages the turbochargers, EGR valves., and DPFs, among other catastrophic failures. 

Therefore, it is important to fix blow-by issues so that your engine can operate with reduced stress, much longer, and more efficiently. To extend the life of your engine, it is advisable to burn fuel clean to reduce exhaust soot. 

How Can I Identify and Test for Engine Blow-By?

For starters, misfiring and rough idling are key indicators of the problem. In case of excessive blow-by, there will be white smoke from the oil-fill tube. You can diagnose this issue by setting the oil-filler cap upside down on the opening. If it immediately blows off, it indicates that there is too much crankcase pressure. 

Another way to tell the issue, that is before the smoke, is a residual oil film around the tube. Blow-by tends to result in contaminated, diluted oil in the engine crankcase.

When your engine is experience excessive blow-by, the mixture tends to cause the diesel to run away upon reaching the combustion chamber. You can check for the diesel engine’s compression by taking a leak-down test. This method helps you determine the amount of blow-by in your engine.

For this process, you will need a compressor and a specialized dual-gauge testing tool with the engine at TDC. The right gauge displays the total amount of air pressure being injected, and the other gauge displays the percentage of pressure being lost. 

How to Fix an Engine Blow-By?

It is always advisable to fix the engine blow before any serious damage and wear occur. There are some tell-tale signs that indicate an engine blow-by, or simply things aren’t right.

These symptoms include excess exhaust smoke, using more oil than usual, starting to breathe heavily, and getting tired and down on power. 

Engine blow-by, oil use, and smoke are all related issues that need immediate attention, failure to which you will have to deal with expensive repairs. 

To reduce engine blow-by, you can do one of two things. Either add FTC Decarbonizer in with your diesel fuel or use flushing oil concentrate when completing an oil change. Most engines may also need some cleaning from the oil side to ensure full cleanliness to the lower piston rings as well. This means running the flushing oil concentrate through the engine. 

Ignoring blow-by for a long time will see to the accumulation of more carbon in the engine. The black smoke will increase, as well as the oil soot. Moreover, fuel efficiency and engine performance deteriorate. The pistons will also undergo rapid wear. 


How can I prevent engine blow-by? 

There are several actions you can take in a bid to prevent blow-by in your engine. For one, preventive maintenance is the best measure. Ensure that your engine is maintained regularly and properly. Also, ensure you use high-quality fluids and oils to keep the engine running smoothly and longer. You can also have oil samples sent to a professional to check for any foreign particulates and residue. 

What are some of the symptoms of engine blow-by?

You will notice several signs that will indicate engine blow-by. You need to look out for sputtering noises from the engine. There will also be white smoke from the oil fill that indicates excessive blow-by. Another sign is a layer of oil film around the tube. Other signs include soot buildup, rough idling or misfiring, and increased oil and fuel consumption. 


An engine affected by a blow-by will not last long. This is because, in the event of an engine blow-by, there is carbon buildup and piston wear. Simply put, engine blow-by can significantly deteriorate your engine’s overall efficiency and performance. This results in costly and time-intensive repairs, and sometimes irreparable damage.